The Four Heavenly Kings, also known as the Dark Four Heavenly Kings (暗黒四天王 in Japanese) are a quartet of alien generals serving under Alien Empera and major antagonists in Ultraman Mebius.
The Four Heavenly Kings were brought together by Alien Empera to serve him in his galactic conquest. Initially comprised of Alien Mefilas, Grozam, Deathrem and King Ark Bogar, they were joined by Yapool after the Emperor sealed Bogar in a black hole.
After Yapool was destroyed by Mebius, Deathrem and Grozam both made attempts to defeat Mebius and both ultimately joined Yapool in his fate.
Alien Mefilas later brainwashed Japan into thinking Mebius was their enemy. After attempting to kill the hypnotized GUYS, Ultraman and Ultraman Mebius both attacked him. Because he couldn't win, Mefilas retreated, but was killed by Empera as punishment.
The Four Heavenly Kings later revived as ghosts in the Monster Graveyard. They attempted to revive Alien Empera using his remains in Mechazam but their plan was foiled and they were destroyed by the Ultra Brothers.